1. Field of the Invention
The present invention relates to an electronic apparatus and battery check method which detect the remaining level of a battery used as a power supply.
2. Description of the Related Art
In recent years, a digital camera and digital video camera are becoming prevalent as image capturing apparatuses. These cameras form an image of light from an object on an image capturing element via an optical lens, thereby capturing and recording a digital image of the object. Such image capturing apparatuses perform a battery check for detecting the remaining battery level from the battery terminal voltage to guarantee the image capturing operation and notify the user of the battery replacement period. Note that the terminal voltage (voltage value) of a battery fluctuates due to, for example, internal resistance characteristic and circuit load. To cope with this situation, there has conventionally proposed a technique for precisely (accurately) detecting the remaining battery level (see Japanese Patent Laid-Open No. 2003-084050).
Japanese Patent Laid-Open No. 2003-084050 stores the consumption currents (consumption current values) of a plurality of circuits in a memory, and detects the battery terminal voltage values in two states different in consumption current, in accordance with each circuit operation condition. The consumption currents of the respective circuits, which are operating in these states, are read out from the memory. Using a value obtained by adding (combining) the readout consumption currents, the battery terminal voltage value in the state of a predetermined consumption current is predicted, thereby detecting the remaining battery level.
For example, a terminal voltage value Vfo of a battery in the state of a predetermined consumption current Ifo is calculated by:Vfo=Vc2′−(Vc1′−Vc2′)·(Ifo−Ic2)/(Ic2′−Ic′)  (1)where Ic1′ is the current value in a first state, Vc1′ is the terminal voltage value of the battery in the first state, Ic2′ is the current value in a second state, and Vc2′ is the terminal voltage value of the battery in the second state.
However, Japanese Patent Laid-Open No. 2003-084050 obtains the current values Ic1′ and IC2′ by adding the consumption currents of the individual circuits, which are operating in the first state and second state and stored in advance. For this reason, when a variation (i.e., a shift (error) from the consumption current stored in the memory) occurs in the actual consumption current of each circuit, an error may be generated in the calculated terminal voltage value Vfo of the battery. Particularly when the difference between the current values Ic1′ and Ic2′ is relatively small, the error of the consumption current value of each circuit has a large adverse influence on the calculation accuracy of the terminal voltage value Vfo of the battery. This makes it difficult to precisely calculate the terminal voltage value Vfo of the battery.
Also, combinations of the consumption current values which constitute the current values Ic1′ and Ic2′ are determined in advance. This limits the timing at which the current values Ic1′ and Ic2′ are predicted to be flowing and the battery terminal voltage value is detected. This, in turn, limits the battery check timing, resulting in a decrease in the degree of freedom of a sequence. In particular, as the circuit scale increases, the timing at which the battery terminal voltage value is detected is more likely to be further limited.